Thanks for the intensive feedback! Everytime the GMTK GameJam starts I think if I should join a team or not, but I'm just too shy/afraid of working with new people I dont know. Maybey I can overcome my fear next time :)
Oh btw, the 2nd upgrade doesnt happen at random! If you level up during a wave you would only receive the upgrade at the end of the wave and not instantly, but if you level 2x time in the same wave you get one upgrade immediately and the 2nd at the end of the wave, its like a buffer.